char *alloc_string(int length);
char *new_empty_string();
char *new_alias_name(const char *tag);
char *new_concat_string(const char *str1, const char *str2);
char *new_head_queue(const char *first_alias);
char *new_tail_part(const char *head_alias, const char *part_alias, const char *tag);
char *new_tail_queue(const char *head_alias, char *tags[]);
char *new_queue(char *tags[]);
